Tom Elliott described the latest talks initiative at Stormont as “the worst” he’d been involved in, as they stumbled to a halt on Sunday night.
The Ulster Unionist MP said the two largest parties – the DUP and Sinn Fein – would have to change their attitude if there was any hope of political progress.
Sinn Fein has said it will not be nominating a deputy first minister on Monday.
Mr Elliott said: “The promises of no return to the status quo have been proven empty by a talks ‘process’ that lacked any structure and had not seen a round table discussion between the five parties as the deadline loomed.
“It was a clear indication that the bigger parties are even more dismissive of the smaller ones than ever, and demonstrates their inability to move away from their old ways.
“We have engaged in every set of recent negotiations from Haass O’Sullivan to today. This was simply the worst.
“Unless there is a massive U-turn in terms of attitude from the two largest parties, then Northern Ireland could be in for a period of prolonged drift.”
He added: ”I understand the secretary of state took the attitude that the blockages to progress were devolved matters and therefore allowed the DUP and Sinn Féin to take the lead, with the government offering support.
“It looks like HM Government will have to take the lead at 4pm tomorrow (Monday) and that is a further indictment of the lead parties at Stormont.”
On Friday, Secretary of State James Brokenshire said: “I believe that a deal is still achievable – with good will, good spirit and that positive intent.
“But time is short. And we must firmly focus on those key issues to enable an Executive to be formed on Monday. It is that task of work that we are firmly engaged in.
“I’ll be working intensively in the coming days to achieve that positive outcome, to see inclusive devolved government restored here in Northern Ireland, that responsibility that we all feel in that regard.”
And on Sunday night, he issued a statement which still attempted to strike a note of optimism.
It said: “Three weeks ago the people of Northern Ireland voted overwhelmingly for effective, devolved, power-sharing government.
“Since then I’ve been working intensively with the political parties and with the Irish government to find a way forward, including putting forward a number of proposals.
“I am determined to see a functioning Executive in place at Stormont. I have spoken to the prime minister this afternoon and this remains the UK government’s continuing priority.”
He concluded: “Even at this stage I urge political parties to agree to work to form an Executive and provide people here with the strong and stable devolved government that they want.”